JP3135683B2 - Spindle motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor using a dynamic bearing used for driving a recording medium.

[0002]

2. Description of the Related Art As devices such as personal computers have become smaller and have higher capacities,
There is also a demand for further miniaturization and higher accuracy of the spindle motor for driving the recording medium incorporated therein. Accordingly, further downsizing and higher accuracy of the spindle motor bearings are also required.

Conventionally, ball bearings are often used as bearings for spindle motors. However, as spindle motors have become smaller, especially smaller outer diameters, the use of ball bearings with smaller outer diameters has required sufficient rotational accuracy because the inner and outer rings are likely to deform during motor assembly. It tends to be difficult in practice. Also, noise and vibration problems are likely to occur. In the case of a spindle motor for driving a recording medium, high-speed rotation is required as the outer diameter is reduced, so that these problems are further promoted. Further, regardless of the size of the outer diameter, the accuracy of the ball bearing is limited and may not satisfy the required specifications.

[0004] Therefore, as a small spindle motor (for example, the outer diameter of the rotor hub is about 40 mm or less), a rotating sleeve portion is provided on the inner peripheral side of the base portion of the substantially hub-shaped rotor hub portion, and the rotating sleeve portion is fixed. 2. Description of the Related Art A spindle motor has been proposed in which a dynamic pressure radial bearing is formed by being externally fitted to a support portion and rotatably supported.

[0005] Generally, a dynamic pressure bearing has low radial rigidity. To increase the rigidity, it is necessary to take measures such as reducing the radial gap or increasing the viscosity of a lubricant. However, when the rigidity is increased by the above-mentioned method, a reaction occurs in which the axial loss also increases. This type of small motor requires high rigidity in the bearing part to withstand vibration and shock.
There is a contradictory problem that it is not possible to cope with low power consumption which is a necessary condition for a small motor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide a sufficient rigidity as a whole and to provide an axial center of a fixed support portion. It is an object of the present invention to provide a spindle motor using a dynamic pressure bearing in which the displacement of the rotation axis of the rotor with respect to the wire is effectively suppressed and the shaft loss is minimized.

[0007]

To achieve the above object, according to the Invention The spindle motor of the present invention includes a rotor hub Ryakuwan shape, a rotary sleeve member, and a fixed post portion, the fixed
The rotating sleeve member rotates automatically via the lubricating oil with respect to the strut.
The outer periphery of the fixed portion A in the axial direction of the rotating sleeve member,
The inside of the fitting hole provided in the base of the rotor hub is fitted and fixed by an interference fit, and another fixed portion B in the axial direction of the rotating sleeve member projects inside the peripheral wall portion of the rotor hub, and the rotating sleeve member is A dynamic pressure radial bearing is formed by being externally fitted to the fixed support and rotatably supported. The fixed portion A of the rotating sleeve member has a smaller radial gap than the fixed portion B and has a fixed radial support. It is designed to be rotatably supported with high rigidity.

Further, in this spindle motor, the cylindrical member is externally fitted and fixed to at least a part of the fixed portion B in the axial direction of the rotary sleeve member by interference fit, so that the fixed portion in the axial direction of the rotary sleeve member is formed. B
In this case, the rigidity of the rotation support by the fixed support portion may be increased.

According to another aspect of the present invention, there is provided a spindle motor including a substantially hub-shaped rotor hub, a rotary sleeve, and a fixed support, wherein the rotary sleeve is externally fitted to the fixed support. The bearing is rotatably supported to form a hydrodynamic radial bearing, and the lubrication disposed in a gap between a fixed pillar portion and a portion of the rotating sleeve portion mainly protruding inside the peripheral wall portion of the rotor hub portion. agent and, disposed in the gap between the inner portion and the fixed support portion of the base portion of the main rotor hub of the rotating sleeve section, than the lubricant
A magnetic fluid seal for separating the highly viscous lubricant is provided over the rotating sleeve portion and the fixed support portion, and a portion of the rotating sleeve portion inside the base portion of the rotor hub portion is formed of the rotating sleeve portion. The fixed support portion is rotatably supported on the fixed support portion with higher rigidity than a portion protruding inside the peripheral wall portion of the rotor hub portion.

[0010]

In a dynamic pressure radial bearing in which a rotating sleeve member (or a rotating sleeve portion) is externally fitted to a fixed support portion, a rotating sleeve member (or a rotating sleeve portion) is provided.
At a fixed portion A in the axial direction and another fixed portion B in the axial direction of the rotating sleeve member (or the rotating sleeve portion) from the rotating sleeve member (or the rotating sleeve portion) and the rotor hub (or the rotor hub portion). Is rotatably supported. According to the first aspect of the present invention, the outer peripheral portion of the fixed portion A in the axial direction of the rotary sleeve member is fitted and fixed to the inside of the fitting hole provided in the base portion of the rotor hub by interference fit. The other fixed portion B projects inside the peripheral wall of the rotor hub, so that the fixed portion A becomes the fixed portion B.
The radial gap is smaller than that of the first embodiment, and it is rotatably supported by the fixed support with high rigidity. For this reason, when the position of the center of gravity in the rotating system is closer to the fixed portion A, the fixed portion A inside the base portion of the rotor hub where the mass distribution in the axial direction of the rotor is large and the shake is likely to occur is relatively high in rigidity. Since the bearing is rotatably supported, the load distribution of the bearing portion is improved, and the displacement of the rotation axis of the rotor with respect to the axis of the fixed support portion is effectively suppressed. In addition, since the other fixed portion B does not need to be rotatably supported with high rigidity, the axial loss as a whole can be minimized.

According to the second aspect of the present invention, the fixed portion A of the rotating sleeve member is fitted and fixed to the fitting hole of the base portion of the rotor hub only by interference fit, and the fixed portion B protrudes inside the peripheral wall portion of the rotor hub. When the rigidity of the rotation support by the fixed support portion is too low, that is, when the position of the center of gravity of the rotating system is close to the fixed portion B side, the cylindrical member is fitted in at least a part of the fixed portion B by fitting. By being externally fixed, the rigidity of the rotation support for the fixed portion B can be optimized according to the load distribution of the bearing portion.

According to the third aspect of the present invention, the lubricant disposed in the gap between the fixed pillar portion and the portion of the rotating sleeve portion protruding inside the peripheral wall of the rotor hub portion, and the base portion of the rotor hub portion in the rotating sleeve portion The lubricant disposed in the gap between the inner portion of the base and the fixed support portion is separated by a magnetic fluid seal. When the position of the center of gravity of the rotating system is closer to the base side of the rotor hub, for example, the base of the rotor hub has a large mass distribution in the axial direction of the rotor and tends to cause blurring. By disposing a lubricant having a higher viscosity than the lubricant disposed in the gap between the fixed column and the portion protruding inside the peripheral wall of the rotor hub in the gap between the fixed column and the protruding portion, Rather, it is rotatably supported on the fixed column with high rigidity. Therefore, the displacement of the rotation axis of the rotor with respect to the axis of the fixed support portion can be effectively suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a spindle motor for driving a hard disk as one embodiment of the present invention. It goes without saying that the spindle motor of the present invention can also be used for driving a rotating body other than a hard disk.

Reference numeral 10 denotes a bracket (fixing portion). The bracket 10 includes a flange portion 10a, an outer peripheral wall portion 10b located inside the flange portion 10a, an annular first bottom portion 10c formed at an inner lower portion of the outer peripheral wall portion 10b, and a first bottom portion 10c.
c, and an annular second bottom 10e formed inside the base of the inner wall 10d.
And The outer peripheral wall 10b and the first bottom 10
An annular concave portion 12 that opens upward is formed by c and the inner peripheral wall portion 10d.

Reference numeral 14 denotes a column-shaped fixed support. The fixed support column 14 projects upward with respect to the bracket 10 with its lower end portion fitted and fixed in a through hole 16 penetrating the center of the second bottom portion 10e. Herringbone grooves 18 and 20 are provided at two locations on the outer peripheral surface, which is the sliding surface of the fixed support 14, at regular intervals in the axial direction. The herringbone grooves 18 and 20 are simply illustrated in such a state that the outer peripheral surface of the fixed column 14 is developed in a plane.

Reference numeral 22 denotes a thrust bearing member, which is externally fitted and fixed to a lower end of a portion of the fixed column 14 protruding above the second bottom portion 10e. Thrust bearing member 22
Has an annular plate shape with an inner peripheral portion projecting slightly downward, and a spiral groove (not shown) is formed on the upper surface which is a slip surface. The outer peripheral portion of the thrust bearing member 22 is provided with a radial gap 21 inside the inner peripheral surface of the inner peripheral wall portion 10d.
The lower surface of the thrust bearing member 22 is separated from the second bottom portion 10e by a gap in the rotation axis direction. 23
Is a lubricant storage space surrounded by the lower surface of the thrust bearing member 22, the second bottom portion 10e, and the inner peripheral wall portion 10d.

The surface shapes of the sliding surfaces of the thrust bearing member 22 and the fixed column 14 are not limited to those described above.

Reference numeral 24 denotes an inner peripheral wall portion 10d of the bracket 10.
The stator core 26 fixed to the outer peripheral wall of the stator core is a stator coil wound around the stator core 24.

Reference numeral 28 denotes a substantially bowl-shaped rotor hub. The rotor hub 28 has an annular base 28a having a fitting hole 30 penetrated in the center, an outer wall 28b hanging down on the outer periphery of the base 28a, and an overhang 28c projecting outward from the outer wall 28b. Have. The overhang portion 28c is provided on the outer
8b occupies about two thirds from the lower end outside.
A plurality of hard disks are externally fitted and fixed to the outer peripheral portion of the outer wall portion 28b and the base portion 28a above the overhang portion 28c by spacers at intervals in the axial direction.

Reference numeral 32 denotes a cylindrical rotor magnet fixed inside the outer wall 28b. Reference numeral 34 denotes a cylindrical rotating sleeve member. This rotating sleeve member 34
An outer peripheral portion of a substantially upper half portion (constant portion A36) excluding an upper end portion is provided with a fitting hole 3 provided in a base portion 28a of the rotor hub 28.
0, it is fitted and fixed coaxially with the rotor hub 28 by an interference fit. A substantially lower half portion (constant portion B38) of the rotating sleeve member 34 projects inside the outer wall portion 28b of the rotor hub 28.

This rotating sleeve member 34 is
A dynamic pressure radial bearing is formed by being externally fitted to and supported rotatably. Of course, the rotating sleeve member 3
A lubricant such as spindle oil is disposed in a gap between the inner peripheral surface of the fixed support 4 and the outer peripheral surface of the fixed column 14. In addition, the lower end surface of the rotating sleeve member 34 is rotatably supported by the upper surface of the thrust bearing member 22 in a space surrounded by the inner peripheral surface of the inner peripheral wall portion 10d of the bracket 10,
A dynamic pressure thrust bearing is configured. It goes without saying that a lubricant such as spindle oil is also disposed in the gap between the lower end surface of the rotating sleeve member 34 and the upper surface of the thrust bearing member 22.

The portion of the overhang portion 28c of the rotor hub 28 other than the upper end portion faces the inner peripheral surface of the outer peripheral wall portion 10b within the annular concave portion 12 with a slight radial gap. The rotor magnet 32 faces the stator core 24 with a radial gap therebetween. The upper end of the fixed column 14 projects above the rotating sleeve member 34.

Reference numeral 40 denotes an annular cushioning member provided from the inner peripheral portion of the upper end surface of the rotor hub 28 to the upper end surface of the rotary sleeve member 34. The upper end surface of the buffer member 40 is located lower than the upper end surface of the fixed column 14, and the inner peripheral portion of the buffer member 40 surrounds the fixed column 14 with a slight radial gap. The buffer member 40 has an annular notch 42 at the lower end inner peripheral portion, and the annular notch 42 and the upper end surface of the rotary sleeve member 34 form a lubricant storage groove 44 that opens radially inward. I have. In addition, as an example of the material of the cushioning member 40, synthetic rubber or the like can be used. Of course, it is not always necessary that the whole portion of the buffer member 40 is made of such a buffer material.

In this spindle motor, for example, the flange 10a of the bracket 10 is fixed to the base 46 of the hard disk drive, and the upper end of the fixed support 14 is fixed to the top plate 50 of the hard disk drive by screws 48. Built into the drive.

The outer peripheral portion of the fixed portion A36 of the rotary sleeve member 34 is fitted and fixed inside the fitting hole 30 formed in the base 28a of the rotor hub 28 by an interference fit, and the fixed portion B38 is fixed to the rotor hub 28. Outer wall 28b
, The inner diameter of the constant portion A36 is
It is slightly smaller than the inner diameter of the fixed portion B38. Therefore, in the dynamic pressure radial bearing, the fixed portion A36 is rotatably supported on the fixed column 14 with higher rigidity than the fixed portion B38.

Mainly, the rotary sleeve member 34, the rotor hub 2
The rotor 52 composed of the rotor 8 and the rotor magnet 32 is rotatably supported by the fixed support 14 with relatively high rigidity at a fixed portion A36 inside the base portion 28a of the rotor hub 28, which has a large mass distribution in the axial direction and tends to cause blur. The rotor 52 with respect to the axis of the fixed support 14 portion.
Of the rotation axis is effectively suppressed.

During transportation of a hard disk drive incorporating the spindle motor or a device including the same, the rotor 52 may slide slightly upward with respect to the fixed support 14 for some reason. However, the impact of the rotating sleeve member 34 against the top plate 50 of the hard disk device and adversely affecting the performance such as the rotation accuracy is prevented by the buffer member 40. The lubricant that leaks from between the upper end surface of the rotary sleeve member 34 and the fixed column 14 mainly during rotation of the spindle motor is
4 to prevent leakage to the outside of the buffer member 40. At least a portion of the leaked lubricant is returned to the gap between the rotating sleeve member 34 and the fixed column 14 due to the rotation stop.

The lower end surface of the rotary sleeve member 34 is
Since the dynamic pressure thrust bearing is constituted by being rotatably supported by the upper surface of the thrust bearing member 22 in the space surrounded by the inner peripheral surface of the inner peripheral wall portion 10d of the bracket 10, the rotating sleeve member 34 Most of the lubricant that leaks almost radially outward from between the lower end face and the thrust bearing member 22 flows down in the radial gap 21 between the inner peripheral surface of the inner peripheral wall portion 10d and the thrust bearing member 22. Thus, the lubricant is stored in the lubricant storage space 23 and is prevented from leaking outside the spindle motor beyond the inner peripheral wall 10d. Further, a lubricant that does not flow down in the radial gap 21 between the inner peripheral surface of the inner peripheral wall portion 10d and the thrust bearing member 22 is also provided.
Inner peripheral wall 10d, stator core 24, stator coil 2
6, rotor magnet 32, outer wall 2 of rotor hub 28
By the effect of the labyrinth seal by the 8b, the overhang portion 28c, the first bottom portion 10c and the outer peripheral wall portion 10b of the bracket 10, the lubricant is prevented from leaking out of the spindle motor, that is, into the hard disk chamber 54.

FIG. 2 is a half sectional view of a spindle motor for driving a hard disk as another embodiment of the present invention.

Due to the dimensions of the members and the physical properties of their materials, if only a fixed portion A36 of the rotary sleeve member 34 is fitted and fixed to the fitting hole 30 of the base portion 28a of the rotor hub 28 by tight fit, the rotary sleeve member 34, rotor hub 2
8. Depending on the position of the center of gravity of the rotating system including the rotor magnet 32 and the hard disk, the rigidity of the rotation support of the fixed column 60 with respect to the fixed portion B38 may be too low as compared with the rigidity with respect to the fixed portion A36. Cannot be prevented.

In this embodiment, the cylindrical member 62 of the rotary sleeve member 34 having a length of about three quarters of the fixed portion B38 protruding inside the outer wall portion 28b of the rotor hub 28 is added to the fixed portion B38. The outer fitting is fixed by an interference fit. Therefore, the inner diameter of the fixed portion B38 is reduced,
Thereby, the fixed strut 60 for the fixed portion B38
, The rigidity of the rotation support is increased, and the displacement of the rotation axis of the rotor 52 with respect to the axis of the fixed support 60 is effectively suppressed.

The meanings of the reference numerals other than the above in FIG. 2 are the same as those in the embodiment shown in FIG.

FIG. 3 is a half sectional view of a spindle motor for driving a hard disk as still another embodiment of the present invention, and FIG. 4 is an enlarged sectional view of a main part thereof.

A circumferential groove 76 is provided on the outer peripheral surface of the fixed support 70 at an outer peripheral portion between two herringbone grooves 72 and 74 provided at a predetermined interval in the axial direction. In the circumferential groove 76, an annular permanent magnet 78 magnetized in the vertical direction and a permanent magnet 7
Annular pole pieces 80 and 82 (made of a ferromagnetic material) that sandwich the upper and lower portions 8 are provided respectively.
The permanent magnet 78 and the pole pieces 80 and 82 can be arranged by appropriately dividing them into arcs. Then, magnetic fluids 84 and 86 are magnetically held between the inner peripheral surface of the rotating sleeve member 34 made of ferromagnetic stainless steel and each of the pole pieces 80 and 82, thereby forming a magnetic fluid seal 87. ing.

In the gap between the rotary sleeve member 34 and the fixed column 70, the portion above the upper magnetic fluid 84, that is, the portion of the rotary sleeve member 34 inside the base 28 a of the rotor hub 28 and the fixed column 70. The lubricant A88 disposed in the gap is disposed below the lower magnetic fluid 86, that is, in the gap between the fixed column 70 and the portion of the rotating sleeve member 34 protruding inside the outer wall 28b of the rotor hub 28. A lubricant having a higher viscosity than that of the lubricant B90 is used. The lubricant A 88 and the lubricant B 90 are separated by the magnetic fluid seal 87. When injecting the magnetic fluids 84 and 86, a pocket injection method can be adopted. First, magnetic fluids 84 and 86 are injected into pockets between the pole pieces 80 and 82 sandwiching the permanent magnet body 78, and then the rotating sleeve member 34 is externally fitted to the fixed support 70.

In this embodiment, the outer periphery of the fixed portion A36 of the rotating sleeve member 34 is connected to the base 28 of the rotor hub 28.
a fixedly fitted inside the fitting hole 30 provided in the hole a, and disposed in the gap between the fixed portion A36 and the fixed support 70 and in the gap between the fixed portion B38 and the fixed support 70. Since the lubricant A88 having a higher viscosity than the lubricant B90 is provided, the fixed support 7 for the portion of the rotary sleeve member 34 inside the base 28a of the rotor hub 28 is provided.
0, the rigidity of the rotation support is further increased.

The rigidity of the rotation support of the fixed post 70 on the inner portion of the base 28a of the rotor hub 28, which has a large mass distribution in the axial direction of the rotor 52 and tends to cause blur, is increased. The effect of suppressing the displacement of the rotation axis of the rotor 52 with respect to

The meanings of the reference numerals other than those described above are the same as those of the embodiment shown in FIG.

[0039]

According to the first aspect of the present invention, a fixed portion A of the rotary sleeve member inside the base of the rotor hub, which has a large mass distribution in the axial direction of the rotor and is liable to cause blur.
In this case, since the rotation is supported with a higher rigidity than the fixed portion B, even if the position of the center of gravity of the rotating system is closer to the fixed portion A, the displacement of the rotation axis of the rotor with respect to the axis of the fixed support portion is effective. To achieve both high shaft rigidity and low shaft loss,
In addition, a dynamic pressure bearing with stable rotation accuracy can be provided.
Therefore, the rotation accuracy can be improved and the recording density when, for example, the recording medium is rotationally driven can be increased, and thus it is suitable as a small-sized spindle motor in which it is difficult to use a ball bearing.

In the spindle motor according to the second aspect of the present invention, when the fixed portion A of the rotary sleeve member is merely fitted and fixed to the fitting hole at the base of the rotor hub by interference fit, the fixed portion B is supported for rotation by the fixed support portion. Part A with constant rigidity
If the rigidity of the fixed portion B is too low compared with the rigidity of the fixed portion A, the rigidity of the rotation support for the fixed portion B can be set to a predetermined ratio with respect to the rigidity of the fixed portion A. Therefore, the displacement of the rotation axis of the rotor with respect to the axis of the fixed support portion can be effectively suppressed.

In the spindle motor according to the third aspect, by changing the viscosity of the lubricant separated by the magnetic fluid seal according to the position of the center of gravity of the rotating system, the rotor can be rotatably supported with rigidity according to the load distribution. For example, of the rotating sleeve member, the inner portion of the rotor hub base where the rotor mass distribution in the axial direction is large and easily causes blurring is rotatably supported with higher rigidity than the portion protruding inside the peripheral wall portion of the rotor hub portion. Therefore, the displacement of the rotation axis of the rotor with respect to the axis of the fixed support portion can be effectively suppressed. Therefore, the rotation accuracy can be improved and the recording density when, for example, the recording medium is rotationally driven can be increased, and thus it is suitable as a small-sized spindle motor in which it is difficult to use a ball bearing.

[Brief description of the drawings]

FIG. 1 is a sectional view.

FIG. 2 is a half sectional view.

FIG. 3 is a half sectional view.

FIG. 4 is an enlarged sectional view of a main part.

[Description of sign]

 14 Fixed Post 28 Rotor Hub 28a Base 30 Fitting Hole 34 Rotating Sleeve Member 36 Constant Part A 38 Constant Part B 62 Tubular Member 87 Magnetic Fluid Seal 88 Lubricant A 90 Lubricant B

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 5/16-5/167 H02K 7/08 F16C 17/10 F16J 15/43

Claims (3)

(57) [Claims] Rotor hub according to claim 1] Ryakuwan shape, it includes a rotary sleeve member, and a fixed post portion, the rotation Sri the fixed strut
A shaft member rotatably supported via lubricating oil, wherein an outer peripheral portion of a fixed portion A in an axial direction of the rotating sleeve member is provided inside a fitting hole provided in a base portion of the rotor hub. The other fixed portion B in the axial direction of the rotating sleeve member projects inside the peripheral wall portion of the rotor hub, and the rotating sleeve member is externally fitted to the fixed support portion and rotatably supported. Thus, a dynamic pressure radial bearing is formed, and the fixed portion A of the rotating sleeve member is more
A spindle motor characterized in that it has a small radial gap and is rotatably supported on a fixed support with high rigidity. 2. A fixed support for the fixed portion B in the axial direction of the rotating sleeve member, wherein the cylindrical member is externally fitted and fixed to at least a part of the fixed portion B in the axial direction of the rotating sleeve member by interference fit. 2. The spindle motor according to claim 1, wherein the rigidity of the rotation support by the portion is increased. 3. A spindle motor comprising a substantially hub-shaped rotor hub, a rotating sleeve, and a fixed support, wherein the rotary sleeve is externally fitted to the fixed support and rotatably supported. Thus, a hydrodynamic radial bearing is formed, and a lubricant disposed in a gap between a fixed pillar portion and a portion of the rotating sleeve portion mainly protruding inside the peripheral wall portion of the rotor hub portion; The lubricant mainly disposed in a gap between an inner portion of a base portion of the rotor hub portion and a fixed support portion.
A magnetic fluid seal is provided over the rotating sleeve portion and the fixed support portion for separating the lubricant having a higher viscosity than the rotating sleeve portion, and a portion of the rotating sleeve portion inside the base portion of the rotor hub portion is provided at the rotating sleeve portion. A spindle motor characterized by being rotatably supported by a fixed support portion with higher rigidity than a portion protruding inside a peripheral wall portion of a rotor hub portion.